epm_207

Okay, I built it. Figured I'd take the pics before launch tomorrow.
Heavily modified Estes EPM-010.

Two stage.
Booster fires on B6-0 central motor and A10-3Ts on the outboard pods.
Sustainer on A8-3 (don't really want this to go very high.)

The outboard pods each have their own streamer. I am estimating that the rocket should stage off the B6-0 AFTER the A10s burn out but well before the A10-3T ejections. The outboard pods also contain streamers which should slow the tumble recovery of the booster and hopefully it will land "bottom first" on the engine, saving the fins.

The nose cones on the tail ends of the pods are just for show. They come off when I load the A10's.

Only concern is that the sustainer will probably be moving at a pretty good clip at ejection. I don't have any A's with a longer delay, though. May go with a long shock cord and some extra elastic.

Fingers crossed.

Wish me luck!

Very cool! That's a pretty good-looking rocket.
I'm glad someone finally decided to try putting motors in the pods!
Oh, and good luck!

BABAR said:

Only concern is that the sustainer will probably be moving at a pretty good clip at ejection. I don't have any A's with a longer delay, though. May go with a long shock cord and some extra elastic.

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That's OK. The zipper due to the short delay will pale in comparison to the cartwheeling, flaming wreck caused by torque steer from the asymmetric thrust of the outboard A10-3T's :wink:

Wish me luck!

Click to expand...

Sure! Good luck

Doug

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This thing is wicked... i hope it flys successfully.. and i hope you have an extinguisher on hand in case this doesnt work out...

Actually flew amazingly well. We have are blessed with a very talented photographer in our group and I will have the pics to prove it (both his talent and that this bird flew!). The outboards gave a real nice smoke trail. Should have gone with a C6-0 in the central booster slot (staged at about 40-50 feet.) Or better yet, designed it to take a D on the central booster slot. I didn't have a good feel for final altitude on this bird (I-m guessing sustainer hit about 500 feet) so didn't want to send it out of this world.

I like the A8 on the sustainer because it has a big nozzle, I always feel a bit more secure with gap staging that some of those glowing coals will successfully navigate the tube and the nozzle to hit the powder on the sustainer motor.

We launched this on the far pad for safety reasons. I concur with other posters, might have been a problem on of the outboards didn't ignite. I think that would be LESS of a problem with a more powerful central engine, but I'm not sure of that.

Very cool. I considered multi-staging mine as well, but ended up just building it stock. I might modify a second one For anybody interested in doing a simpler two stage, my sims showed that an additional 6g of nose weight would allow it to fly with the original design and stock fins, separating just behind the small strakes. This is with an 18mm motor in the booster and 13mm in the sustainer.

FWIW I often use the mini A3-4T motors in sustainers and have never had an issue with one igniting. Even with an adapter it's lighter than an A8-3 and a longer delay.

pick1e said:

Very cool. I considered multi-staging mine as well, but ended up just building it stock. I might modify a second one For anybody interested in doing a simpler two stage, my sims showed that an additional 6g of nose weight would allow it to fly with the original design and stock fins, separating just behind the small strakes. This is with an 18mm motor in the booster and 13mm in the sustainer.

FWIW I often use the mini A3-4T motors in sustainers and have never had an issue with one igniting. Even with an adapter it's lighter than an A8-3 and a longer delay.

Click to expand...

I'm going to have to learn to use sim programs. I am curious ---- with the 6 grams of nose weight, is the sustainer stable as a stand alone launch vehicle with those small stock fins? I am guessing (although suspect that would not be a good idea to rely on it) that sustainers have an advantage of already having significant velocity at time of staging, thus their fins are already more effective than a rocket coming off the pad. Am I correct that the velocity at staging is probably greater than most rockets at the tip of the launch rod?

I like the idea of using the mini-motors, I need to get or make some adapters for them that still keep the lower weight advantage.

Current project is the MIRV Gryphon. The idea isn't new (Estes has a MIRV), this will be single C6-0 (or D12-0) in the booster going to 3 A4-3T sustainers. I am testing the waaaaaaaaaay off-center fins. Sort of like a square version of the Jon Rocket Corkscrew.
Fingers crossed.

Thanks for the help.

Tom

BABAR said:

Okay, I built it. Figured I'd take the pics before launch tomorrow.
Heavily modified Estes EPM-010.

Two stage.
Booster fires on B6-0 central motor and A10-3Ts on the outboard pods.
Sustainer on A8-3 (don't really want this to go very high.)

The outboard pods each have their own streamer. I am estimating that the rocket should stage off the B6-0 AFTER the A10s burn out but well before the A10-3T ejections. The outboard pods also contain streamers which should slow the tumble recovery of the booster and hopefully it will land "bottom first" on the engine, saving the fins.

The nose cones on the tail ends of the pods are just for show. They come off when I load the A10's.

Only concern is that the sustainer will probably be moving at a pretty good clip at ejection. I don't have any A's with a longer delay, though. May go with a long shock cord and some extra elastic.

Fingers crossed.View attachment 101511View attachment 101512View attachment 101513View attachment 101514View attachment 101515

Wish me luck!

Click to expand...

I'd really like to copy this one to the gallery if I may.

BABAR said:

I am curious ---- with the 6 grams of nose weight, is the sustainer stable as a stand alone launch vehicle with those small stock fins?

Click to expand...

Yes, that's how I came up with the 6g. Basically drew up the sustainer with an A3-4T in it, and added nose weight until it was stable enough to fly solo.

BABAR said:

I am guessing (although suspect that would not be a good idea to rely on it) that sustainers have an advantage of already having significant velocity at time of staging, thus their fins are already more effective than a rocket coming off the pad. Am I correct that the velocity at staging is probably greater than most rockets at the tip of the launch rod?

Click to expand...

Yes, much greater velocity. My sims show the sustainer on my Comanche-3 staging at something like 175mph. I've learned that they still need to be stable, but you can get much closer to marginal.

BABAR said:

I like the idea of using the mini-motors, I need to get or make some adapters for them that still keep the lower weight advantage.

Click to expand...

Mine are simply a length of BT-5, a couple 5/20 centering rings, and a thrust ring. If you make it the same overall length as an 18mm motor, standard motor hooks will retain the whole assembly:

View attachment 102400

Wow, nice looking!

JAL3 said:

I'd really like to copy this one to the gallery if I may.

Click to expand...

Wow. Absolutely. I hope to have a launch photo posted soon.